An Enhanced Pfafstetter Catchment Reference System

The Pfafstetter system delineates and codes hierarchically nested catchments. Its simple coding scheme denotes stream network position, enabling systematic analysis of the impacts of any activity on a river section without need for a GIS. However, widespread application has identified significant limitations. Issues raised include an inability to code complex drainage systems or large numbers of endorheic basins, the variability in both the levels of basin decomposition and subbasin sizes and main stem identification criteria not conforming to local understanding. To address these issues, the Pfafstetter system was modified to use an independent regionalization for the initial subdivision of the continent. New procedures were developed to code distributary drainage networks and endorheic basins and alternate criteria devised to identify the main stem and to produce a more even decomposition of a catchment. These modifications were successfully applied to the task of delineating and coding hierarchically nested catchments for the Australian continent including its complex distributary and anabranching drainage networks and large numbers of endorheic basins. The independent basin grouping produced initially smaller and more evenly sized subbasins and modeled estimates of flow identified the main stem correctly slightly more often than the original contributing area criterion. Enabling further subdivision of catchments with fewer than four tributaries produced the largest change in catchment delineations, doubling the number of subbasins and halving their size. Achieving the vision for a comprehensive basin reference system will require further development to include anthropogenic and other hydrological features not controlled by topography. Key Points Five modifications to the widely adopted Pfafstetter system for continent‐wide catchment analysis are described and tested Altering the stopping rule for basin decomposition had the greatest impact on both the size and numbers of subbasins Other enhancements enable coding of the topological relationships of distributary streams and endorheic basins